A power system is a network of components used to supply, transmit and/or use electric power. Generally, the power system includes generator sets (gensets), that are self-contained power modules that can be permanently or temporarily connected to an offboard facility, such as a home, a hospital, or a factory, to provide primary, supplemental, and emergency backup power to one or more external loads.
In some situations, an overcurrent condition may occur within the power system. The overcurrent condition may occur due to an overload of the power system, or due to a short circuit within the generator of the power system (an internal short circuit) or a short circuit somewhere outside of the generator of the power system (an external short circuit) of the power system. Certain regulating codes require over current and short circuit protection for power systems both inside and outside of the power system. In addition, the regulating codes require the power system under an overcurrent condition to be able to supply current long enough to allow an overcurrent protection device (e.g., a circuit breaker) closest to the location where an external short circuit exists to trip. This is called selective coordination and is important for providing power to life critical facilities such as hospitals. Selective coordination may require the power system to continue to supply current for several minutes. However, continuing to supply current to a load when the power system has an internal short circuit may greatly increase the risk of fire within the power system, thus increasing the risk of damaging components of the power system other than the ones initially involved in the short circuit. In certain circumstances, there is a risk that the fire may start in as little at 1/10th of a second after the internal short circuit occurs.
U.S. Pat. No. 7,521,822 (the '822 patent) to Lorenz, published on Nov. 13, 2008, discloses a method for protecting gensets from overcurrent. Specifically, the '822 patent discloses a protection technique for a back-up electric power generation system having generator control circuitry. The technique includes receiving sensor signals representative of electric output of an electric power generator, and determining if a shut-down condition exists, as a function of a protection profile pre-determined for the system.
But, the system of the '822 patent may not differentiate internal short circuits from external short circuits. The system of the '822 patent merely keeps current from exceeding an arbitrary time versus current curve chosen to limit insulation aging from excessive heat generation. The system of the '822 patent may not react fast enough to internal short circuits to inhibit damage to the system. In addition, since the system of the '822 patent relies on current measurement outside of the generator, the system may not be able to identify short circuits in the generator itself.
The disclosed power system having a short circuit protection controller is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.